NED Abstract

Copyright by European Southern Observatory (ESO).
Reproduced by permission
2012A&A...538A.152Z
Radio properties of H_2_O maser host galaxies
Zhang, J. S.; Henkel, C.; Guo, Q.; Wang, J.
Abstract. The 6 cm and 20 cm radio continuum properties of all 85 galaxies
with reported 22 GHz H_2_O maser emission and luminosity distance D > 0.5
Mpc are studied. For the total of 55 targets for which both 6 cm and 20 cm
measurements exist and for the subsample of 42 sources with masers related
to active galactic nuclei (AGN), a spectral index could be determined from
an assumed power-law dependence. The mean value of the resulting spectral
index is in both cases 0.66 +/- 0.07 (S is proportional to {nu}^-{alpha}^;
S: flux density, {nu}: frequency). Comparing radio properties of the maser
galaxies with a sample of Seyferts without detected H_2_O maser, we find
that (1) the spectral indices agree within the error limits; and (2) maser
host galaxies have higher nuclear radio continuum luminosities, exceeding
those of the comparison sample by factors of order 5. Only considering the
subsample of galaxies with masers associated with AGN, there seems to be a
trend toward rising maser luminosity with nuclear radio luminosity (both
at 6 cm and 20 cm). However, when accounting for the Malmquist effect, the
correlation weakens to a level, which is barely significant. Overall, the
study indicates that nuclear radio luminosity is a suitable indicator to
guide future AGN maser searches and to enhance detection rates, which are
otherwise quite low (<10%).
Key words: galaxies: active, radio continuum: galaxies, galaxies: nuclei,
masers, radio lines: galaxies